I hate to reinvent the wheel - Date/time differences

Question

Does anyone have a concise SQL algorithm to find the difference between
2 dates and times where the dates are stored in a date field and the times are stored as a varchar in the format HH:MM:SS (24 hr clock).

Answer 1

Hi,
I am using a stored procedure which give calculates the no of days between two dates. Try using/modifying it and see if it is of any help
The Procedure................
DECLARE
     vdDateFrom DATE;
     vnDayFrom NUMBER := 0;
     vnMonthFrom NUMBER := 0;
     vnYearFrom NUMBER := 0;
     vdDateTo DATE;
     vnDayTo NUMBER := 0;
     vnMonthTo NUMBER := 0;
     vnYearTo NUMBER := 0;
     vnYearsDiff NUMBER := 0;
     vnMonthsDiff NUMBER := 0;
     vnDaysDiff NUMBER := 0;
     E_STOP EXCEPTION;
BEGIN
     vdDateFrom := '01/11/2001';
     dbms_output.put_line('Date From: '||vdDateFrom);
     vdDateTo := '17/11/2001';
     dbms_output.put_line('Date To: '||vdDateTo);
     IF vdDateTo < vdDateFrom THEN
          RAISE E_STOP;
     END IF;
     vnDayFrom := to_char(vdDateFrom, 'dd');
     vnMonthFrom := to_char(vdDateFrom, 'mm');
     vnYearFrom := to_char(vdDateFrom, 'yyyy');
     vnDayTo := to_char(vdDateTo, 'dd');
     vnMonthTo := to_char(vdDateTo, 'mm');
     vnYearTo := to_char(vdDateTo, 'yyyy');
     IF vnMonthTo - vnMonthFrom < 0 THEN
          vnYearsDiff := vnYearTo - vnYearFrom - 1;
     ELSIF vnMonthTo - vnMonthFrom > 0 THEN
          vnYearsDiff := vnYearTo - vnYearFrom;
     ELSE
          IF vnDayTo - vnDayFrom >= 0 THEN
               vnYearsDiff := vnYearTo - vnYearFrom;
          ELSIF
               vnDayTo - vnDayFrom < 0 THEN
               vnYearsDiff := vnYearTo - vnYearFrom - 1;
          END IF;
     END IF;
     dbms_output.put_line('Years: '||vnYearsDiff);
     IF vnMonthTo - vnMonthFrom < 0 THEN
          IF vnDayTo - vnDayFrom >= 0 THEN
               vnMonthsDiff := 12 + vnMonthTo - vnMonthFrom;
          ELSIF
               vnDayTo - vnDayFrom < 0 THEN
               vnMonthsDiff := 12 + vnMonthTo - vnMonthFrom - 1;
          END IF;
     ELSIF vnMonthTo - vnMonthFrom = 0 THEN
          IF vnDayTo - vnDayFrom >= 0 THEN
               vnMonthsDiff := 0;
          ELSIF
               vnDayTo - vnDayFrom < 0 THEN
               vnMonthsDiff := 11;
          END IF;
     ELSE
          IF vnDayTo - vnDayFrom >= 0 THEN
               vnMonthsDiff := vnMonthTo - vnMonthFrom;
          ELSIF
               vnDayTo - vnDayFrom < 0 THEN
               vnMonthsDiff := vnMonthTo - vnMonthFrom - 1;
          END IF;
     END IF;
     dbms_output.put_line('Months: '||vnMonthsDiff);
     IF vnMonthFrom = vnMonthTo THEN
          vnDaysDiff := vnDayTo - vnDayFrom;
     IF vnDaysDiff < 0 THEN
     vnDaysDiff := to_char(last_day(add_months(vdDateTo,-1)),'dd') - vnDayFrom;
               IF vnDaysDiff < 0 THEN
                    vnDaysDiff := vnDayTo;
               ELSIF vnDaysDiff >= 0 THEN
                    vnDaysDiff := vnDaysDiff + vnDayTo;
               END IF;
     END IF;
     ELSE
          vnDaysDiff := vnDayTo - vnDayFrom;
     IF vnDaysDiff < 0 THEN
     vnDaysDiff := to_char(last_day(add_months(vdDateTo,-1)),'dd') - vnDayFrom;
               IF vnDaysDiff < 0 THEN
                    vnDaysDiff := vnDayTo;
               ELSIF vnDaysDiff >= 0 THEN
                    vnDaysDiff := vnDaysDiff + vnDayTo;
               END IF;
     END IF;
     END IF;
     dbms_output.put_line('Days: '||vnDaysDiff);
EXCEPTION
     WHEN E_STOP THEN
     dbms_output.put_line('Error: Date To is less than Date From.');
END;
Regards
Dinesh